1. Technical Field
The present disclosure is directed to perfluoroisopropyl-substituted perfluorophtalocyanines, including zinc (II), copper (II) and oxo-vanadium (IV) complexes of 29H,31H,1,4,8,11,15,18,22,25-octakis-fluoro-2,3,9,10,16,17,23,24-octakis-perfluoro(isopropyl)phthalocyanine (F64Pc). The disclosed ligand exhibits bulky i-C3F7 (Rf) peripheral groups. Alternative complexes include alternative transition metal constituents and TiO. The disclosed compounds/molecules can be sublimed under high vacuum conditions. In addition, the disclosed compounds/molecules produce advantageous thin films (20-100 nm) on glass substrates by physical vapor deposition. Many potential applications of the disclosed compounds/molecules are disclosed, e.g., as semiconductor materials and in devices.
2. Background Art
Phthalocyanines (Pc) have long proven to be of high interest in both basic research and practical applications due to their electrical and optical properties [1]. Metallated macrocyclic metal complexes such as PcM, are of considerable value because of the numerous possibilities of chemical modifications of both the central metal and organic ligand, viz., the ring substituents. Their electrical properties are of particular interest, provided crystals and thin films can be obtained. Even though the charge carrier mobility in PcM thin films is typically lower than in many other molecular semiconductors, crystals of phthalocyanines that showed a field-effect mobility of up to 1 cm2V−1s−1 have been grown.
Chemical modification of phthalocyanines leads to systematic changes in both their redox potential and molecular configuration, opening the possibility of detailed tuning of the structure and energy levels in the solid state. One approach to modifying phthalocyanines is aimed at the metal core, the nature of which can be varied and to which a variety of axial ligands can be attached. Axial ligands range from single atoms, such as halogen and oxygen, present for example in PcV═O, PcTi═O, PcInCl and PcAlF, to organic groups such as methyl, ethyl, pyridine, or fluorophenyl. A second path to new Pc complexes is to vary the ring substituents. For example, F-atoms can be introduced to modify the periphery of the Pc ligand, leading to partly (F4Pc [2], F8Pc [2], F14.5Pc [3,4]) or perfluorinated phthalocyanines (F16Pc [5]). Both the metal centers (and their axial ligands), as well as the ring substituents, induce a variety of solid-state architectures, as revealed, for example, by single-crystal X-ray structure determinations.
In addition to packing forces present in the crystalline state, the assembly of the same materials, evaporated to produce thin films, is further influenced by the choice of substrate (e.g. metal, inorganic oxide insulator, organic polymer insulator) as well as the evaporation conditions [3-11]. Fluorination can alter not only the crystal structure but also the growth mode of thin films prepared from fluorinated phthalocyanines [11-13]. Thus, it is notable that, independent of the work of the inventor herein, with the exception of a monochlorinated Pc [14], no single-crystal X-ray structure of ring-halogenated PcM could be found in the Cambridge Structural Database, despite the fact that many halogenated phthalocyanines were reported. Of further note, ring halogenation may not result in a major deviation from planarity, and frequently allows the formation of conductive films in the monolayer thickness range whose electronic properties are distinct from those of films prepared from non-halogenated phthalocyanines, especially with respect to intermolecular coupling.
The presence of electron-withdrawing ring substituents, such as halogens, lowers the energy of the molecular orbitals (MOs), including the frontier orbitals over a wide range. This effect was indicated for a number of phthalocyanines, including those bearing F-groups, by quantum chemical calculations of isolated molecules, by the observed shifts of the electrochemical potential of molecules in solution and by shifts of the ionization energy obtained by photoelectron spectroscopy for molecules in the gas phase. Even though additional solid-state effects are superimposed on molecular changes, the trends observed for individual molecules are clearly preserved in thin films, as exemplified by the ease of reduction and, hence, observed n-type conduction for fluorinated phthalocyanines. In particular, F16Pc materials are interesting candidates for n-type channels in organic field effect transistors, being relatively stable even under ambient conditions. A further step in the direction of orbital stabilization is represented by the introduction of perfluorinated alkyl groups as Pc ring substituents.
If applicable to a given molecule, vapor deposition has turned out to be a valuable method of film preparation for organic semiconductor thin films because of a high degree of purity and because a structural control can be established. Aside from unsubstituted Pc only few substituted Pcs like fluoro-substituted F4Pc, F8Pc, F14.5Pc or F16Pc can be vapor deposited.
Despite efforts to date, a need remains for additional compounds/molecules that provide and/or support advantageous applications, including thin film applications, and associated methods for synthesis thereof. These and other needs are satisfied by the advantageous compounds/molecules disclosed herein, as well as methods for synthesis and applications of such compounds/molecules.